Fibrillar collagens are biosynthesized as procollagens with both amino- and carboxy-terminal globular extension peptides. Type II procollagen has two alternative splice forms of the amino-propeptide that either contains a cysteine-rich domain (von Willebrand C) encoded by exon 2 (type IIA) or does not contain exon 2 (type IIB). Type IIA procollagen is present in embryonic basement membranes, developing heart, spine and chondroprogenitor cells while type IIB procollagen is synthesized almost exclusively by chondrocytes (Sandell et al., 1993). The mRNA splice switch from type IIA to IIB procollagen is a sign of commitment to chondrogenesis, or cartilage formation.
Cartilage is avascular and resistant to tumor invasion. A better understanding of the mechanisms that keep cartilage avascular and resistant to tumor invasion may help develop compositions and methods for inducing cell death and inhibiting angiogenesis. Due to the prevalence of tumor related and angiogenesis related disorders, there is a need in the art for methods for inducing cell death and inhibiting angiogenesis.